This invention relates generally to grippers and specifically to a powered gripper having a moving arm and a blocking member.
Automated or powered grippers have been commonly used to grip or retain work pieces, such as sheet metal, polymeric parts and the like in checking fixtures, gauging stations, welding stations and punching machines. Such grippers have also been used to transfer work pieces between stations when mounted to a robotic arm.
Many existing grippers are powered by hydraulic or pneumatic fluid devices. Furthermore, known grippers often employ one or more moving arms which move in response to piston-type actuation. Examples of such grippers are disclosed in U.S. Pat. Nos. 5,516,173 entitled "Gripper" which issued to Sawdon on May 14, 1996 (the disclosure of which is hereby incorporated herein by reference); as well as in U.S. Pat. Nos. 5,072,652 entitled "Gripping Device Having Impact Cushioning Means" which issued to Blatt on Dec. 17, 1991; 3,635,514 entitled "Dual Grip Automation Jaw Swivel Assembly" which issued to Blatt on Jan. 18, 1972; and 3,013,835 entitled "Power Operated Jaw Assembly" which issued to Blatt on Dec. 19, 1961.
It has recently become desirable to prevent the gripper arms from opening if there is a loss of fluid pressure. It would also be desirable to mechanically limit the movement of the gripping arms in various positions independent of the inaccuracies of fluid pressure upon the piston. It would further be desirable to easily interchange differing gripper pad configurations. However, many traditional grippers fail to fully achieve these desired features.
In accordance with the present invention, a preferred embodiment of a universal gripper has a movable arm locked in a gripping position by abutting against a movable blocking member. In another aspect of the present invention, a pair of pivoting arms are maintained in their gripping positions by a blocking member being linearly slid between ends of the arms. In a further aspect of the present invention, varying movable arm configurations can be easily interchanged with each other and mounted to a body by way of a single fixed pivot pin. In yet a further aspect of the present invention, the opening angle of a gripper arm can be mechanically limited to various positions by selective positioning of an adjustment member. Moreover, another aspect of the present invention adjustably mounts a stop onto an external surface of a body for protecting a gripper arm from damage. An additional aspect of the present invention employs a partially cylindrical gripping pad shape for achieving easy interchangeability of differently configured pads.
The universal gripper of the present invention is highly advantageous over traditional grippers in that the moving gripper arms can be maintained in their gripping positions even during loss of piston fluid pressure. This eliminates undesired opening of the gripper arms which can lead to inadvertent dropping and damage of the workpiece. The specific shapes of the arms as well as the ability to move the blocking member relative to the body and arms allow for improved precision and control of the arm movements, smoother and less "jerking" movement of the components so as to reduce stress and premature failure. The present invention further provides for a more compact assembly, reduced manufacturing and raw material costs by eliminating component parts, while insuring precise and repeatable gripping pressure on the workpiece whether or not fluid pressure is applied to the piston.
The present invention is also advantageous by maximizing linear and pivoting mechanical advantages to supply superior gripping force; for example, 80 pounds per square inch of pneumatic force at the piston has been found to produce between 300 and 500 pounds of gripping force. Additionally, the arms can be easily interchanged between various fixed and pivoting configurations by removing only one otherwise fixed pivot pin. Moreover, a variety of gripping pads are interchangeably mounted upon the specifically configured arms. The arms and pads can be reconfigured within three minutes by pulling a single pin or by removing a single screw, respectively. This allows for quick changes so as to minimize expensive down time while being adapted for many workpieces. The specific shape and fastening of the universal gripper pads encourage easy installation and very secure mounting while being adjustment free, thereby further minimizing down time while improving gripper precision, which leads to improved workpiece positioning and processed quality. Additional advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.